Any communications network, regardless of whether it utilizes optical or electromagnetic signals, is susceptible to a variety of occurrences that can impact the health of the system. System health includes parameters that reflect the performance, efficiency and security of signal transmission. In particular, networks can experience component failure, signal interference, and intrusive access by unauthorized parties. Systems and methods of monitoring system health have been employed to predict, prevent, and to detect these network irregularities.
One approach taken by many system health monitoring protocols is to transmit a “supervisory,” “test,” or “monitoring” signal having a known characteristic, and then to check the characteristics of the signal when it is received at another point on the network. Some examples of these types of systems are disclosed in U.S. Pat. Nos. 5,345,230 to Jackson, 5,483,233 to Pettit, 5,712,937 to Asawa, 5,825,515 to Anderson, 5,894,362 to Onaka, 5,937,032 to Nummelin, and 5,055,827 to Philipp. For example, the Jackson patent describes a method of applying a signal having a known characteristic to an optical transceiver, coupling its transmitter to its receiver, and comparing the characteristics of the resulting output signal to those of the known input signal, thereby verifying the proper operation of the transceiver and the communication link.
However, such an approach of monitoring has several disadvantages. For one, the supervisory signal consumes valuable bandwidth. In addition, these systems also consume resources in transmitting, detecting, and processing the supervisory signals. Furthermore, some systems using the supervisory signal methodology also employ a series of repeaters stationed along the system that aid in the determination of the location of the irregularity, and possibly the device involved. This added facet requires the additional expense and labor involved with installing a repeater whenever a new device is placed into service.
An approach adopted in Ethernet systems is to detect collisions of data packets that have been transmitted concurrently from more than one node. When a collision is detected, the problem may be resolved by causing all network nodes to temporarily cease transmission while the system recovers. Such an approach may ensure the successful delivery of data packets, but otherwise does not provide much useful information on the health of a network. An example of this type of system is disclosed in U.S. Pat. No. 5,185,735 to Ernst. The Ernst patent describes a LAN noise monitor that detects positive voltage on LAN cable. Upon detecting positive voltage on the LAN cable, the LAN noise monitor indicates the presence, and possibly the amount, of noise to a LAN sentinel. However, the LAN sentinel of Ernst can only determine the presence and approximate location of LAN noise if a number of nodes are electrically connected to the LAN cable through LAN noise monitors.
There are also approaches that monitor other inherent characteristics of the communications transmissions themselves, such as diffraction of the signals, signal strength, wavelength, depolarization, change in phase, or nonlinear processes. A common feature in these approaches is the establishment of a threshold level, which if exceeded, indicates the presence of a problem. However, without positioning expensive repeaters or reflectometers strategically along the system, the location and source of the fault cannot be readily determined. An example of this approach is described in U.S. Pat. No. 5,471,342 to Junginger. The Junginger patent discloses monitoring an amplifier by measuring the scattered light coming from a splice area. However, the method of Junginger is directed to monitoring at a specific location, rather than monitoring an entire network or network segment.
Because of a desire to allocate bandwidth and to identify nodes on a network, networks typically have some administrator whose sole job is to oversee operation of the network. The administrator may oversee the physical components of the network, such as the network medium, network cards, the nodes, as well as any hubs, repeaters, switches, or bridges. Additionally, the administrator manages the addition or deletion of nodes from the network and the accompanying change in addressing. The administrator also performs maintenance, upgrades, and other periodic work on the network. The administration of a network can therefore be rather costly to an organization.
Considering the foregoing, what is needed is the ability to identify the location and nature of network irregularities that bear upon system health, without decreasing bandwidth that is available to the network. There is further need to implement a comprehensive means of monitoring without adding redundant and expensive equipment to the network.